Development of Advanced Technologies for Mixed Natural Gas Detection

Abstract

Advanced technologies for mixed gas detection are discussed. A calorific measurement technique for hydrogen-natural gas mixtures using ultrasonic transducers is examined. Measuring the speed of sound in the gas medium enables an accurate composition testing of mixed gas. At the beginning, different ultrasonic transducers are tested and a suitable one for gas testing is chosen. A jig is designed to conduct the testing with nitrogen/oxygen mixtures in a proof of principle experiment. Another jig is designed and manufactured to test a transit time ultrasonic method for flow rate calculation in order to obtain a full energy flow measurement. A mixed gas leak detection technique based on laser spectroscopy is also studied. A Mid-Wave Infrared (MWIR) laser is implemented to be used as a source in a direct absorption measurement for methane detection. The implemented MWIR laser uses nonlinear optics to generate a MWIR output. A novel intracavity structure using periodically poled lithium niobate as the nonlinear crystal is implemented, and the highest blackbox efficiency for continuous wave difference frequency generation in the MWIR region is reported, to the best of our knowledge. Currently the output power is around 8.1 mW at 3.5 μm with a 1.058% W-1 blackbox efficiency. Watt level MWIR generation is expected using an optimized setup. At last, a second laser source that operates in the long-wave infrared (LWIR) region was also studied. The discussed laser setup for LWIR generation is similar to the MWIR one with different pump and signal wavelengths and an orientation patterned gallium phosphide (OP-GaP) as the nonlinear crystal. Due to the absorption loss of GaP at the pump wavelength, only mW power level is expected out of the intracavity structure. Some alternative approaches for LWIR generation are discussed.